Method for peening

ABSTRACT

To provide a peening processing method which is superior in practical use and may perform a peening process extremely effectively and uniformly. In a peening processing method in which slurry into which liquid and shots are mixed and pressurized air are mixed to form injection material, the injection material is injected from an injection port of a nozzle so that the shots in the injection material are collided against a workpiece whereby mechanical characteristics of a surface of the workpiece are changed, the nozzle and the workpiece are moved relative to each other so that the injection material is injected to a predetermined region of the surface of the workpiece, furthermore, as the nozzle, the injection port is a slit-like injection port that is wide in a direction perpendicular to a relative moving direction of the nozzle and the workpiece and the nozzle having a structure where the injection material is injected in a parallel flow from the overall region of the slit-like injection port is adopted.

TECHNICAL FIELD

The present invention relates to a peening processing method.

BACKGROUND ART

As a process applied to a workpiece made of metal, a peening process(also called shot peening or the like) has been proposed in which anumber of balls called shots (which are not always spherical) areinjected at a high speed against a surface of the workpiece from aninjection port of a nozzle to thereby collide a number of shots on thesurface of the workpiece, and the surface of the workpiece is formedinto a pear skin pattern by the collision of a number of shots, thusenhancing the surface hardness of the workpiece, prolonging a fatigueservice life, enhancing an anti-wear property or decreasing a fluidresistance.

In this peening process, it is important to increase the collisionenergy of the shots to some extent (unless the collision energy is low,the increase of a compression residual stress in the vicinity of thesurface of the workpiece or a depth at which the maximum residual stressoccurs, which is important for the peening process, would beinsufficient so that the effect by the peening process is degraded) andto collide the shots against the surface of the workpiece as uniformlyas possible (if this is non-uniform, as a matter of course, the surfacehardness of the workpiece or the like would become non-uniform).

Also, this peening process is categorized into two kinds of processes,i.e., a so-called dry blast method in which shots are injected simply bypressurized air and a so-called wet blast method in which shots aremixed with water and kept under a slurry condition and the slurry isinjected by pressurized air. The latter process rather than the formerprocess has the advantage such that the amount of splash shot is smalland the working management is easy or because the pressurized air iskept under a condition surrounded by the slurry film, the accelerationby the expansion of the pressurized air is well applied to the shots tothereby increase the collision energy and so on.

By the way, in a conventional peening process, as shown in FIGS. 1(a)and 1(b), a so-called round nozzle having a circular injection port 22is adopted as a nozzle and this round nozzle 21 is moved relative to theworkpiece 23 so that the shots (slurry) injected from the injection port22 of the round nozzle 21 is injected to the overall surface of theworkpiece 23.

Also, if only the single nozzle 21 is used, as a matter of course, ittakes long time to process a wide area. Accordingly, in some cases, aplurality of round nozzles 21 are juxtaposed and used (for example, inthe condition that three round nozzles are juxtaposed).

However, the conventional peening processing method using the roundnozzles 21 has the following disadvantage.

The injection port 22 of the round nozzle 21 is set up at apredetermined diameter or more so that the shot may be collided againsta wide area to some extent. Accordingly, since the injection port 22 hasthe predetermined diameter or more, the shots to be injected from theinjection port 22 are diffused radially as shown in FIG. 1(a) andcollided against to the workpiece 23.

The thus radially diffused shots are collided substantially in acircular shape on the surface of the workpiece 23 as shown in FIG. 1(b).Accordingly, if the peening process is carried out while moving theround nozzle 21 relative to the workpiece 23 (the moving direction ofthe nozzle 1 in FIG. 1(b) is indicated by reference numeral 26), since awidth in the moving direction is large in a region indicated byreference numeral 24 in FIG. 1(b) on the surface of the workpiece 23,the shots are collided for a long period of time correspondingly,whereas since the width in the moving direction is short in a regionindicated by reference numeral 25 in FIG. 1(b) (regions near the endportions in a direction perpendicular to the moving direction of theround nozzle 21), the shots are collided for a short period of timecorrespondingly. Accordingly, the numbers of collisions of the shotsagainst the workpiece 23 are different depending upon a place so thatthe peening process becomes non-uniform.

Furthermore, in case of the round nozzle 21, the shots are biased on theside of the circumferential wall of the injection port 22 due to theexpansion effect of the pressurized air (so-called doughnut phenomenon).Thus, the shots are collided in a doughnut shape onto the surface of theworkpiece 23. As expected, the peening becomes non-uniform.

Furthermore, since the region near the center of the injection port 22and the region around this region are different in distance from theinjection port 22 to the surface of the workpiece 23 due to theabove-described diffusion, necessarily, the collision energy isdifferent to thereby make the peening process non-uniform.

For this reason, for example, it is possible to adopt a method in whichthe distance between the injection port 22 and the workpiece 23 is keptlong to thereby decrease the difference (rate) in collision energy ofthe shots as much as possible. However, in this case, as a matter ofcourse, it is necessary to kept the processing space wide.

Also, it is possible to adopt a method in which the two adjacent roundnozzles 21 are positioned close to each other so that the shots injectedfrom the nozzles 21 are collided in a region where a small number ofshots collide each other. However, this method is a method in whichafter all, the same region is subjected to the peening process by usingthe two round nozzles 21 and is an extremely ineffective method.

Furthermore, in case of this method, since the shots injected from thetwo round nozzles 21 are collided against each other, the collisionenergy is degraded when the shots are collided against the workpiece, itis likely that the peening process would be non-uniform and theinjection energy of the shots is lost.

Also, in order to prevent the diffusion of the shots, it is possible topropose a method in which the injection path of the shots within theround nozzle 21 is elongated. However, in this case, there is a problemthat the nozzle 21 is enlarged in size or a problem that the injectionvelocity of the shots is degraded due to the frictional resistancebetween the inner wall of the injection path and the shot andnecessarily, the above-described collision energy is decreased.

In order to solve the above-noted problems, as a result of the repeatedexperiments, the present invention is a technology to confirm andestablish that a nozzle having a wide injection port is adopted wherebythe peening process may be performed extremely effectively anduniformly.

DISCLOSURE OF THE INVENTION

The essence of the invention will now be described with reference to theaccompanying drawings.

A peening processing method in which slurry into which liquid and shotsare mixed and pressurized air are mixed to form injection material 9,the injection material 9 is injected from an injection port 2 of anozzle 1 so that the shots in the injection material 9 are collidedagainst a workpiece 3 whereby mechanical characteristics of a surface ofthe workpiece 3 are changed, is characterized in that the nozzle 1 andthe workpiece 3 are moved relative to each other so that the injectionmaterial 9 is injected to a predetermined region of the surface of theworkpiece 3, furthermore, as the nozzle 1, the injection port 2 is aslit-like injection port 2 that is wide in a direction perpendicular toa relative moving direction of the nozzle 1 and the workpiece 3 and thenozzle 1 having a structure where the injection material 9 is injectedin a parallel flow from the overall region of the slit-like injectionport 2 is adopted.

Also, the peening processing method according to claim 1 is furthercharacterized in that a nozzle 1 for injecting the injection material 9uniformly from an overall region of the slit-like injection port 2 isadopted as the nozzle 1.

Also, the peening processing method according to claim 1 is furthercharacterized in that the injection material 9 is injected from a normaldirection of the surface of the workpiece 3 as much as possible.

Also, the peening processing method according to claim 2 is furthercharacterized in that the injection material 9 is injected from a normaldirection of the surface of the workpiece 3 as much as possible.

Also, the peening processing method according to any one of claims 1 to4 is further characterized in that the injection material 9 is injectedfrom a normal direction of the surface of the workpiece 3 as much aspossible while both the nozzle 1 and the workpiece 3 are moved.

Also, a peening processing method in which slurry into which liquid andshots are mixed and pressurized air are mixed to form injection material9, the injection material 9 is injected from an injection port 2 of anozzle 1 so that the shots in the injection material 9 are collidedagainst a workpiece 3 whereby mechanical characteristics of a surface ofthe workpiece 3 are changed, is characterized in that both the nozzle 1and the workpiece 3 are moved relative to each other so that theinjection material 9 is injected to a predetermined region of thesurface of the workpiece 3, furthermore, as the nozzle 1, the injectionport 2 is a slit-like injection port 2 that is wide in a directionperpendicular to a relative moving direction of the nozzle 1 and theworkpiece 3 and the nozzle 1 having a structure where the injectionmaterial 9 is injected in a parallel flow from the overall region of theslit-like injection port 2 is adopted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) is an illustrative perspective view of a conventional example.

FIG. 1(b) is an illustrative enlarged plan view of a surface of aconventional workpiece 23.

FIG. 2 is an illustrative perspective view of the present embodiment.

FIG. 3 is an illustrative side elevational cross-sectional view.

FIG. 4(a) is a model view of a slurry for theoretically illustrating adegree of effective utilization of shots in Experimental Example 1.

FIG. 4(b) is an illustrative enlarged view of a surface of the workpiece3 under the condition of 100% coverage.

FIG. 4(c) is a model view in the case where in Experimental Example 1,100% shots are uniformly collided against the surface of the workpiece3.

BEST MODE FOR EMBODYING THE INVENTION

FIGS. 2 to 4 show one embodiment of the present invention and will nowbe described.

In the embodiment, in a peening processing method in which slurry intowhich liquid (water) and shots (for example, glass balls) are mixed andpressurized air are mixed to form injection material 9, the injectionmaterial 9 is injected from an injection port of a nozzle 1 so that theshots in the injection material 9 are collided against a workpiece 3(for example, fins of an air-craft engine) whereby mechanicalcharacteristics of a surface of the workpiece 3 are changed, a method isadopted in which the nozzle 1 and the workpiece 3 are moved relative toeach other (for example, the workpiece 3 is moved relative to the nozzle1 or the nozzle 1 is moved to the workpiece 3) so that the injectionmaterial 9 is injected to a predetermined region of the surface of theworkpiece 3, and furthermore, as the nozzle 1, the injection port 2 is aslit-like injection port that is wide in a direction perpendicular to arelative moving direction of the nozzle 1 and the workpiece 3 and thenozzle 1 having a structure where the injection material 9 is injectedin a parallel flow from the overall region of the slit-like injectionport 2 is adopted.

The workpiece 3 is maintained in an upright condition on a rotary jig 5.

The workpiece 3 is rotated under the upright condition by the rotationof this rotary jig 5.

The nozzle 1 is arranged so as to be moved back and forth, up and downand right and left relative to the workpiece 3. The shots may beinjected over the full surface of the workpiece by the rotation of therotary jig 5 and the movement of this nozzle 1.

Also, the nozzle 1 is arranged so as to be slanted relative to theworkpiece 3 as desired so that the shots (injection material 9) may beinjected in a normal direction of the shot injected surface of theworkpiece 3 as much as possible by the slant.

The rotation of the rotary jig 5 and the movement and the slant of thenozzle 3 are controlled in a concentrated manner by an NC control(numerical control) so that the injection of the shots to the workpiece3 may be performed in a proper manner. Also, the rotation of the rotaryjig 5 and the movement and the slant of the nozzle 3 are selected sothat the distance from the slit-like injection port 2 of the nozzle 1 tothe surface of the workpiece 3 may be kept substantially constant.

Also, the nozzle 1 is arranged so as to inject uniformly the shots fromthe overall region of the slit-like injection port 2.

Also, a mixture portion (not shown) for mixing the slurry and thepressurized air is incorporated into the nozzle 1. A guide injectionpath 6 having a predetermined length in which the injection direction ofthe shots (slurry) is straight as much as possible is provided from themixture portion to the slit-like injection port 2.

The width of the slit-like injection port 2 is set up to a width bywhich the shots may be injected over the full surface of a predeterminedportion (a desired portion to be peened) of the workpiece 3 for a shotperiod of time as much as possible. Incidentally, the width of theslit-like injection port 2 may exceed the width of the workpiece 3.

In the drawings, reference numeral 7 designates a slurry supply portionand numeral 8 designates a pressurized air supply portion.

A result of each experiment of the present embodiment will now bedescribed.

EXPERIMENTAL EXAMPLE 1

A nozzle 1 having a slit-like injection port 2 which was 100 mm wide and2.5 mm long was used.

Glass balls (commercial name: “M-10” made of Potters/Barotini Co.)having a granular size of about 150 to 90 μm were used as the shots.

The shots were handled under the slurry condition mixed with water. Aconcentration of the shots in the slurry was set at 40%.

A pump pressure of the pressurized air was set at 0.3 MPa and a slurryflow rate was set at 10 liter/min, respectively, so that the shots wereinjected to the workpiece 3 at a pressure of 0.4 MPa.

When the experiments were repeated under those conditions, it wasconfirmed that a condition of 100% coverage at an intensity of 2.1 mm (acondition that the shots are uniformly collided every one time over thesurface (surface to be machined) of the workpiece 3) could be realizedat a peening processing velocity of 200 mm/s (according to a measurementof an intensity measurement instrument).

By the way, if it is assumed that the shots in the slurry be arrangedand aligned in a rectangular body as shown in FIG. 4(a) and an averagegranular size of the shots be 120 μm, the slurry amount Qs flowing forone second means the slurry amount per one minite/60 seconds=10(liter)/second=0.166 (liter)=166 cm³/sec), and the number of shots ninjected for one second is Qs×concentration of the shots/volume of shots(in terms of a cubic body)=166 (cm³/second)×40(%)/(120 (μm))³=38425926(pieces/second), i.e., about 40 million pieces/second.

On the other hand, when the surface of the workpiece 3 kept under this100% coverage condition was observed by a microscope, it was confirmedthat the collision damage of average granular size of 25 μm (see FIG.4(b)).

If one piece of shot may form a collision damage of 25 μm, the lengththrough which the shots of 38425926 pieces/second may form the collisiondamage over the full surface of the workpiece 3 having the width of 100mm is (shot number/(100 (mm)/diameter of collision damage)/length ofcollision damage=(38425926 (pieces/sec)/(100 (mm)/25 (μm)))=240(mm/second). Namely, theoretically, if 100% shots may collide onto thesurface of the workpiece 3 uniformly, it is possible to perform thepeening process on the workpiece 3 having the width 100 mm over 240 mmfor one second (peening processing velocity Vs=240 mm/s. see FIG. 4(c)).

According to the foregoing experimental example 1, the actually measuredpeening processing velocity was 200 mm/s. This value is about 83% of thetheoretical peening processing velocity Vs=240 mm/s. Accordingly, it issafe to say that it was confirmed that the shots were collided againstthe workpiece 3 at an extremely high efficiency rate in the embodiment.

In contrast, in the conventional method using the round nozzle 21, asdescribed above, the number of the effective shots collided against theworkpiece 23 is considered very low for the reasons why the shots arecollided only for a short period of time at the end portions (indicatedby reference numeral 25 in FIG. 1(b)) in the direction perpendicular tothe moving direction of the round nozzle 21, the shots are biased on theside of the circumferential wall of the injection port 22 of the roundnozzle 21 due to the expansion effect of the pressurized air (doughnutphenomenon), the central portion of the injection port 22 and theperipheral portion thereof are different in distance from the injectionport 22 to the surface of the workpiece 23 and also different incollision energy due to the diffusion of the shot (injection material)and so on.

EXPERIMENTAL EXAMPLE 2

The peening process was applied to an SUS plate (workpiece) having ahardness HV45, which was 80 mm long, 2 mm wide and 1 mm thick. A warpage(intensity) of this SUS plate was measured by a dial gauge. The resultswere compared between the method according to this embodiment (describedas a wide gun in the table) and the conventional method using the roundnozzle (described as a round gun in the table).

A nozzle having a slit-like injection port that is 60 mm wide and 2.5 mmlong was used as the wide gun and a nozzle having a circular injectionport having an inner diameter 12.7 mm was used as the round gun.

The experiments were repeated while varying the moving velocity of thenozzle (gun) to the workpiece and the air pressure for injecting theslurry containing the shots.

The experimental results are shown in Table 1 and Table 2.

In order to meet the conditions of the coverage 100% and the intensity2.1 mm at 1.0 second (the condition that the variation of the intensitywas suppressed within 10% even by the continuation of the peeningprocess), the wide gun needed the air pressure of 0.25 MPa and the roundgun needed the air pressure of 0.45 MPa.

Namely, according to Experimental Example 2, it was confirmed thataccording to this embodiment, it was possible to effectively perform thepeening process even at a low air pressure (low output), that is, it waspossible to perform the peening process at a high efficiency rate.

By the way, from the results of Experimental Example 2, the efficiencyof this embodiment and that of the conventional method were comparedwith each other.

This comparison was made under the condition of substantially the sameintensity and process velocity and the 100% coverage, i.e., at O sign inTables 1 and 2.

The process conditions according to this embodiment were as follows: Airpressure 0.25 MPa Air consumption rate 2,030 Nl/min Slurry flow rate 6.8L/min Process effective width 50 mm

The process conditions according to the conventional method were asfollows: Air pressure 0.45 MPa Air consumption rate 860 Nl/min Slurryflow rate 27.8 L/min Process effective width 8 mm

Incidentally, the intensity was about 2.1 mm and the process velocitywas 70 mm/sec. These are substantially the same.

Presumably, in the comparison in process time, {process area accordingto wide gun}/{process area according to round gun} was (70 (mm/sec)×50(mm))/(70 (mm/sec)×8 (mm))=6.25. Namely, the process speed according tothis embodiment was 6.25 times higher than that according to theconventional method.

Comparing the air amount needed for this process time, since6.25:1=2,030 (Nl/min):860 (Nl/min), the needed air amount according tothis embodiment was 6.25 times less than that according to theconventional method. Accordingly, it is safe to say that the pressurizedair was effectively consumed according to this embodiment.

Also, comparing the shot amount needed for the process time (at the sameshot concentration in the slurry), since 6.25:1=6.8 (L/min):27.8(L/min), the present embodiment needed only one 25.6th of theconventional method. Accordingly, it is safe to say that the shots wereextremely effectively consumed according to the present embodiment.

As described above, according to Experimental Example 2, it wasconfirmed that according to the present embodiment, the process speedwas high even if the pressure of the pressurized air was low, andfurthermore, the pressurized air and the shots (slurry) could beextremely effectively utilized.

EXPERIMENTAL EXAMPLE 3

This was substantially the same example as Experimental Example 2 butthe warpage of each portion of the workpiece was measured.

Also, the air pressure for injecting the slurry containing the shotswere set so as to warp the workpiece substantially to the same extent bythe wide gun and the round gun.

Also, the experiments were repeated while varying the moving velocity ofthe nozzle to the workpiece.

The experimental results are shown in Table 3 below.

It was conformed that in the round gun (conventional), the machiningamount was considerably different between the right and left sideportion (peripheral edge portions) in the direction perpendicular to themoving direction and the central portion, whereas in the wide gun (thisembodiment), the difference in machining amount was small between theright and left side portion in the direction perpendicular to the movingdirection and the central portion and in addition the average region wasextremely wide.

Namely, according to Experimental Example 3, it was confirmed that inthis embodiment, it was possible to attain the uniform peening process,and particularly, it was very effective in the case here the workpiecewas subjected to the area process.

Incidentally, according to the conventional method using the round gun,it is necessary to further apply the peening process to the right andleft side portions in the direction perpendicular to the movingdirection where the machining amount is insufficient. However, it isvery troublesome and hard to inject the shots (injection material 9) sothat the machining amount in the right and left side portions and themachining amount in the central portion are kept substantially the same.

EXPERIMENTAL EXAMPLE 4

The peening process was performed while varying the air pressure and thesurface roughness was measured.

The same wide gun as that of Experimental Example 2 was used. Two kindsof the round guns, i.e., the same round gun as that of ExperimentalExample 2 (described as round gun ½ in the table) and the round gunhaving the circular injection port having an inner diameter of 9.7 mm(described as round gun ⅜ in the table) were used.

The distance between the injection port and the workpiece was a minimumdistance through which the peening process might be performed uniformly(which was a confirmation result by a preliminary experiment).

The experimental result is shown in Table 4 below.

It was confirmed that the surface roughness was large substantially inproportion to the elevation of the air pressure by the wide gun but theelevation of the surface roughness was slow down when the elevation ofthe air pressure by the round gun reached some extent or more.

Namely, according to Experimental Example 4, it was confirmed that inthis embodiment, even if the air pressure was high, it was possible toeffectively perform the peening process, and accordingly, it waspossible to perform the peening process at a high speed and at a highefficiency rate.

Incidentally, according to the conventional method using the round gun,in the case where the air pressure was high, the energy loss wasremarkable, and it was difficult to perform the peening process at ahigh speed and at a high efficiency rate.

According to each experimental result, it was confirmed that the presentembodiment was superior in energy efficiency and shot efficiency, it waspossible to extremely uniformly perform the peening process and as aresult, the process speed was high.

As described above, according to the present embodiment, it is possibleto provide a peening processing method that is superior in practical useand in which it is possible to collide the shots within the injectionmaterial 9 injected against the workpiece 3 at an extremely highefficiency rate, thereby shortening the peening process time and savingthe energy for injecting the shots.

Also, since the shots (injection material 9) are not excessivelyinjected, it is possible to prevent, without fail, any fragile fractureof the workpiece 3 due to the excessive application of the peeningprocess (overpeening which would occur at about the coverage 600).

Also, since the shots are effectively collided against the workpiece 3,the wear of the shots is prevented due to the fact that the shots arecollided against each other, thus making it possible to attain the longservice life of the shots.

Also, since the shots are injected uniformly in a parallel flow from theslit-like injection port 2, unlike the case where a plurality of roundnozzles are juxtaposed, there is no injection bias of the shots in thewidth direction of the nozzle 1, as a matter of course, thereby makingit possible to perform the uniform peening on the surface of theworkpiece 3.

Also, because of the method to perform the peening process while movingboth the nozzle 1 and the workpiece 3, it is possible to set thepositional relation between the nozzle 1 and the workpiece 3 rapidly andsuitably. Also in this sense, it is possible to perform the peeningprocess for a short period of time.

INDUSTRIAL APPLICABILITY

When the experiments of the peening process adopting the method in whichthe nozzle 1 and the workpiece 3 are moved relative to each other sothat the injection material 9 (the mixture of the pressurized air andthe liquid into which the shots are mixed) is injected to apredetermined portion of the surface of the workpiece 3 and furthermore,the injection material 9 is injected from the slit-like injection port 2that is wide in the direction perpendicular to the above-describedrelative moving direction and the above-described nozzle 1 has astructure in which the injection material 9 is injected in the parallelflow from the overall region of the slit-like injection port 2 areconducted, it is confirmed that the shots are uniformly collided on thesurface of the workpiece 3 for an extremely short period of time(confirmed by a measurement instrument for measuring the peeningcondition).

Presumably, this is the reason why, since the injection port 2 is theslit-like injection port 2 that is wide in the direction perpendicularto the above-described relative moving direction, unlike the roundnozzle, the shots are uniformly collided onto the surface of theworkpiece 3 in the direction perpendicular to the above-describedrelative moving direction, and furthermore, and since the injectionmaterial 9 is injected in a parallel flow from the overall region of theslit-like injection port 2, also in this point, the shots within theinjection material 9 are uniformly collided against the surface of theworkpiece 3 so that it is unnecessary to collide the shots whiledirecting the injection port of the nozzle to the same portion manytimes.

Counting the effective utilization rate of the shots, the shots werecollided effectively to the surface of the workpiece 3 at an extremelyhigh effective consumption rate that was about 80%.

Also, since the effective utilization rate of the shots is high, as amater of course, it is possible to save the injection energy of theshot. Furthermore, it is possible to prevent the injection of the extrashots while shortening the time to peen. It is therefore possible toavoid, without fail, the condition that the number of the collision ofthe shots is excessive to reduce the surface hardness (overpeened).

As described above, according to the present invention, it is possibleto provide a peening processing method that is superior in practical usewhich may perform extremely effectively the peening process uniformly.

1. A peening processing method in which slurry into which liquid and shots are mixed and pressurized air are mixed to form injection material, the injection material is injected from an injection port of a nozzle so that the shots in the injection material are collided against a workpiece whereby mechanical characteristics of a surface of the workpiece are changed, characterized in that the nozzle and the workpiece are moved relative to each other so that the injection material is injected to a predetermined region of the surface of the workpiece, furthermore, as a nozzle, the injection port is a slit-like injection port that is wide in a direction perpendicular to a relative moving direction of the nozzle and the workpiece and the nozzle having a structure where the injection material is injected in a parallel flow from the overall region of the slit-like injection port is adopted.
 2. The peening processing method according to claim 1, further characterized in that as the nozzle, a nozzle having a structure where a mixture portion for mixing the slurry and the pressurized air is provided in an inner portion, and a guide injection path having the same cross-section as a cross-section of the wide slit-like injection port and having a predetermined length by which the injection direction of the injection material is straight as much as possible is provided until the slit-like injection port corresponding to the workpiece width from the mixture portion is adopted.
 3. The peening processing method according to claim 2, further characterized in that a nozzle for injecting the injection material uniformly from an overall region of the slit-like injection port is adopted as the nozzle.
 4. The peening processing method according to claim 3, further characterized in that the injection material is injected from a normal direction of the surface of the workpiece as much as possible.
 5. The peening processing method according to claim 4, further characterized in that the workpiece is retained under an upright condition to a rotary jig and rotated under the upright condition by the rotation of the rotary jig.
 6. The peening processing method according to claim 5, further characterized in that the nozzle is slanted relative to the workpiece as desired.
 7. The peening processing method according to claim 6, further characterized in that the nozzle may be moved back and forth, up and down and right and left relative to the workpiece.
 8. The peening processing method according to claim 7, further characterized in that the movement and slant of the nozzle and the rotation of the rotary jig are controlled so that the distance from the injection port of the nozzle to the surface of the workpiece may be kept substantially constant. 